The records of fossil fishes in the Denbighshire Coalfield appear even more scanty than those of the molluscs, and one of the first references1 is to a fish-bed in the roof of the “ Queen Coal ” at Llay Hall Colliery in the north of Denbighshire. This coal is 300–400 feet from the bottom of the Middle Coal Measures, and is known as the “ Premier ” in Flintshire, and in South Denbighshire as the “ Wall and Bench ”. Throughout Denbighshire it is the lowest generally worked seam of the productive measures, as the coals below it are few and, in any case, too thin for profitable operation, except when in association with pottery clay.